Airgap-containing interconnect structure with patternable low-k material and method of fabricating

ABSTRACT

An interconnect structure is provided that includes at least one patterned and cured low-k dielectric material located on a surface of a patterned inorganic antireflective coating that is located atop a substrate. The inorganic antireflective coating comprises atoms of M, C and H wherein M is at least one of Si, Ge, B, Sn, Fe, Ta, Ti, Ni, Hf and La. The at least one cured and patterned low-k dielectric material and the patterned inorganic antireflective coating have conductively filled regions embedded therein and the at least one cured and patterned low-k dielectric material has at least one airgap located adjacent, but not directly in contact with the conductively filled regions.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/473,789, filed May 17, 2012, now abandoned, which is a divisional ofU.S. patent application Ser. No. 11/971,470, filed Jan. 9, 2008, nowU.S. Pat. No. 8,476,758 issued on Jul. 2, 2013, the entire content anddisclosure of which are incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to an interconnect structure and a methodof fabricating the same. More specifically, the present inventionrelates to an interconnect structure including a patternable dielectricmaterial as an interconnect dielectric and at least one airgap withinthe patternable dielectric material. The present invention also providesa method of fabricating such a patternable dielectric interconnectstructure.

BACKGROUND OF THE INVENTION

It is widely known that the speed of propagation of interconnect signalsis one of the most important factors controlling overall circuit speedas feature sizes are reduced and the number of devices per unit area aswell as the number of interconnect levels are increased. Throughout thesemiconductor industry, there has been a strong drive to increase theaspect ratio (i.e., height to width ratio) and to reduce the dielectricconstant, k, of the interlayer dielectric (ILD) materials used toelectrically insulate the conductive metal lines. As a result,interconnect signals travel faster through conductors due to a reductionin resistance-capacitance (RC) delays.

State-of-the-art semiconductor chips employ copper (Cu) as theelectrical conductor and inorganic organosilicates as the low dielectricconstant (low-k) dielectric, and have up to twelve levels of Cu/low-kinterconnect layers. These Cu/low-k interconnect layers are fabricatedwith an iterative additive process, called dual-damascene, whichincludes several processing steps. For example, a typical dual-damasceneprocess includes film deposition, patterning by lithography and reactiveion etching, liner deposition, Cu metal fill by electrochemical plating,and chemical-mechanical polishing of excessive Cu metal; these steps aredescribed in greater detail in the following paragraphs.

When fabricating integrated circuit wiring within a multi-layeredscheme, an insulating or dielectric material, e.g., silicon oxide or alow-k insulator will normally be patterned with several thousandopenings to create conductive line openings and/or via openings usingphoto patterning and plasma etching techniques, e.g., photolithographywith subsequent etching by plasma processes. The via openings aretypically filled with a conductive metal material, e.g., aluminum,copper, etc., to interconnect the active and/or passive elements of theintegrated circuits. The semiconductor device is then polished to levelits surface.

A continuous cap layer is then normally deposited over the planarizedsurface featuring the dielectric material and conductive metallicmaterial. Next, a dielectric material is deposited over the continuouscap layer, via and line openings are created within the dielectric layeras before, another conductive metal material is deposited within theopenings and another continuous cap layer is deposited thereon. Theprocess is repeated to fabricate a multi-layer interconnect wiringsystem. The multi-layer interconnect system built thereby is referred toin the art as a dual-damascene integration scheme.

Unfortunately, the strategy to introduce low-k materials (typicallydielectrics whose dielectric constant is below that of silicon oxide)into advanced interconnects is difficult to implement due to the newmaterials chemistry of the low-k materials that are being introduced.Moreover, low-k dielectrics exhibit fundamentally weaker electrical andmechanical properties as compared to silicon oxide. Moreover, the low-kdielectric alternatives are typically susceptible to damage during thevarious interconnect processing steps. The damage observed in the low-kdielectric materials is manifested by an increase in the dielectricconstant and increased moisture uptake, which may result in reducedperformance and device reliability.

One way to overcome the integration challenges of low-k materials is toprotect these low-k dielectric materials by adding at least onesacrificial hardmask layer onto a surface of the low-k dielectricmaterial. While the hardmask layer serves to protect the low-k material,the presence of the sacrificial hardmask layer adds enormous processcomplexity as more film deposition, pattern transfer etch, and removalof hardmask layers are needed.

A state-of-the-art back-end-of-the-line (BEOL) integration process,called a low temperature oxide (LTO) process, employs up to eight layersof sacrificial hardmask materials to fabricate a two-layerdual-damascene interconnect structure.

For example, a via-first LTO integration for forming a dual-damasceneinterconnect includes the steps of: depositing a dielectric material ona substrate including a patterned conductor; forming at least one via insaid dielectric material, such that at least one of the vias ispositioned over the patterned conductor; depositing a layer ofplanarizing material on the dielectric material and in the via;depositing a layer of barrier material on the layer of planarizingmaterial; depositing at least one layer of imaging material on the layerof barrier material; forming at least one trench in the imagingmaterial, barrier material and planarizing material, such that the atleast one trench is positioned over the via; removing the imagingmaterial, either after or concurrently with forming the trench in theplanarizing material; transferring the at least one trench to thedielectric material, such that at least one of the trenches ispositioned over the via; removing the barrier material, either after orconcurrently with transferring the at least one trench to the dielectricmaterial; and removing the planarizing material.

A line-first LTO integration for forming a dual-damascene interconnectstructure includes the steps of: depositing a dielectric material on asubstrate including a patterned conductor; forming at least one trenchin the dielectric material, such that the at least one trench ispositioned over the patterned conductor; depositing a layer ofplanarizing material on the dielectric material and in the trench;depositing a layer of barrier material on the layer of planarizingmaterial; depositing at least one layer of imaging material on the layerof barrier material; forming at least one via in the imaging material,barrier material and planarizing material, such that at least one of thevias is positioned over the trench and the patterned conductor; removingthe imaging material, either after or concurrently with forming the viain the planarizing material; transferring the at least one via to thedielectric material, such that at least one of the vias is positionedover the trench and the patterned conductor; removing the barriermaterial, either after or concurrently with transferring the at leastone via to the dielectric material; and removing the planarizingmaterial.

The integration schemes, such as the LTO one mentioned above, are verycomplex, inefficient, and costly. For example, the via-first LTOintegration scheme requires ten layers of films and twenty-one processsteps to form a two-layer dual-damascene dielectric structure. In otherwords, 80% of the films are not needed in the final interconnectstructure.

Although immensely popular in semiconductor manufacturing, the prior artdual-damascene integration scheme described above suffers from severaldrawbacks including:

-   -   (I) First, it constitutes a signification portion of        manufacturing cost of advanced semiconductor chips as many        layers, up to twelve layers for the state-of-the-art chips, are        required to connect the minuscule transistors within a chip and        to the printed circuit board.    -   (II) Second, it is a main yield detractor as the many layers of        films required to form the interconnects generate chances for        defect introduction and, thus, degrade manufacturing yields.    -   (III) Third, it is very inefficient and embodies enormous        complexity. The current dual-damascene integration scheme        requires many sacrificial films (80% of the film stack) to        pattern and protect the fragile interlayer dielectric films from        damage during processing. These sacrificial patterning and        protective films have to be removed after patterning and copper        plating.    -   (IV) Fourth, the performance gain by introduction of new lower-k        materials is often offset by the needs for higher-k        non-sacrificial materials, such as a cap layer, a hardmask        layer, or a thicker copper barrier layer.    -   (V) Fifth, the prior art complex dual-damascene process        lengthens manufacturing turn-around time and R&D development        cycle.    -   (VI) Sixth, the plasma etching process is an expensive and often        unreliable process and requires significant up-front capital        investment.

In view of the above, there is a need to simplify the formation ofinterconnects (single-damascene and dual-damascene) including low-kdielectrics for cost-saving and manufacturing efficiency. This is alsotrue in interconnect structures in which at least one airgap is present.

Airgaps are typically used in the prior art as means for lowering theeffective dielectric constant of the interconnect structure. Lower theeffective dielectric constant of an interconnect structure is importantin the semiconductor industry since such structures have lowerresistance associated therewith. In prior art interconnect structures,airgaps are introduced into the structure utilizing many additionalprocessing steps which raise the production cost of the structure beingmanufactured. As such, a new method of providing an airgap-containinginterconnect structure is also needed which avoids the numerous stepsthat are used in the prior art for fabricating such an interconnectstructure.

SUMMARY OF THE INVENTION

The problems described above in prior art processes of fabricatingairgap-containing interconnect structures are solved by using adramatically simplified integration method of this invention. Thepresent invention thus relates to a method of forming airgap-containinginterconnect structures that are part of integrated circuits andmicroelectronic devices with patternable dielectrics combined with aparticular antireflective coating.

This invention circumvents the prior art drawbacks of currentintegration by combining the functions of a photoresist and a dielectricmaterial into one material. This one material, called aphoto-patternable low-k dielectric (or patternable low-k material forshort), acts as a photoresist during the lithographic patterningprocess, and as such, no separate photoresist is required. Afterlithographic patterning, the patternable low-k dielectric issubsequently converted into a low-k material during a post patterningcure. In this way, the inventive method avoids plasma etching and thecomplex sacrificial film stack and processes required for patterning.After lithographically patterning the patternable low-k dielectric ofthe invention, the pattern within the patternable low-k dielectric isfilled with a conductive material and then planarized. At least oneairgap is then introduced into the patternable low-k dielectric materialin a region adjacent to, but not directly abutting, the conductivelyfilled regions of the patternable low-k dielectric material. The airgapextends above the upper surface of the patternable low-k dielectric andinto and through a dielectric capping layer located above theconductively-filled patternable low-k dielectric material. An airgap capis then formed atop the dielectric capping layer essentially sealing thetop of the airgap from other interconnect levels that may be formed atopthis level of the interconnect structure.

In the inventive method, an antireflective coating layer is required forpatterning of a patternable low-k material via lithography.Unfortunately, conventional organic antireflective coatings aregenerally not suitable for the lithography of a patternable low-kmaterial as the antireflective coating layer is a permanent part of theinterconnect structure. These organic antireflective coatings typicallycannot withstand high temperature processes such as, for example, thehigh temperature during either the curing of the patternable low-kdielectric or annealing of the interconnect metal.

Thus, the present invention employs an antireflective coating forlithography and interconnect integration of patternable low-k materials.The antireflective coating that is employed in the present invention isa permanent part of the airgap-containing interconnect structure and isan inorganic material that is formed by vapor or liquid phase depositionincluding, for example, chemical vapor deposition (CVD), plasma enhancedchemical vapor deposition (PECVD), physical vapor deposition (PVD), andatomic layer deposition (ALD), spin-on coating, spray coating, dipcoating.

The inorganic ARC employed in the present invention is a compositionthat includes atoms of M, C and H, wherein M is at least one of Si, Ge,B, Sn, Fe, Ta, Ti, Ni, Hf and/or La. The inorganic ARC may optionallyinclude atoms of O, N, S, F or mixtures thereof. In some embodiments, Mis preferably Si.

Specifically, this invention relates to a simplified method offabricating an interconnect structure including at least one airgaplocated within at least one patternable dielectric that is located atopthe inorganic ARC mentioned above.

In general terms, the method of the present invention includes:

providing at least one patternable low-k material on a surface of aninorganic antireflective coating (ARC) that is located atop a substrate,said inorganic ARC comprises atoms of M, C and H wherein M is at leastone of Si, Ge, B, Sn, Fe, Ta, Ti, Ni, Hf and La;

forming at least one interconnect pattern within said at least onepatternable low-k material, said at least one interconnect pattern isformed without utilizing a separate photoresist material;

curing said at least one patternable low-k material into a dielectricmaterial having a dielectric constant of not more than 4.3;

filling said at least one interconnect pattern with a conductivematerial;

forming a stack comprising a dielectric cap and a block mask locatedatop said at least one cured patternable-low-k dielectric material;

forming at least one airgap through said stack and into said at leastone cured patternable low-k dielectric material; and

forming an airgap cap atop said dielectric cap of said stack.

In some embodiments of this method of the present invention, theantireflective coating (ARC) further includes atoms of X, wherein X isone of O, N, S and F. In another embodiment of the present invention, adielectric cap is formed on top of the substrate prior to forming theARC.

The present invention also contemplates a step of forming contact holesthrough the antireflective coating or material stack including theantireflective coating and the dielectric cap after forming theinterconnect patterns.

In yet a further embodiment of the present invention, the conductivematerial is Al, Cu, or a Cu alloy. A planarization process such aschemical mechanical polishing may follow the step of filling theinterconnect patterns.

In any of the embodiments mentioned above, the interconnect patterns maycomprise via openings, line openings, a combination of via openingslocated beneath line openings or a combination of line openings locatedbeneath via openings. In one embodiment, it is preferred to have viaopenings located beneath line openings. It is noted that in the presentinvention each individual pair of line/via openings or via/line openingsis interconnected.

The present invention contemplates the use of positive-tone patternablelow-k materials, negative-tone patternable low-k materials or anycombination thereof.

In a preferred embodiment of present invention, the inventive methodincludes the steps of:

providing a first patternable low-k material on a surface of aninorganic antireflective coating (ARC) that is located atop a substrate,said inorganic ARC comprises atoms of M, C and H wherein M is at leastone of Si, Ge, B, Sn, Fe, Ta, Ti, Ni, Hf and La;

forming first interconnect patterns within the first patternable low-kmaterial without a separate photoresist;

providing a second patternable low-k material on top of the firstpatternable low-k material including said first interconnect patterns;

forming second interconnect patterns within said second patternablelow-k material without a separate photoresist;

curing at least said second patternable low-k material;

filling said first and second interconnect patterns with a conductivematerial;

forming a stack comprising a dielectric cap and a block mask locatedatop said cured second patternable low-k dielectric material;

forming at least one airgap through said stack and into at least saidcured second patternable low-k dielectric material; and

forming an airgap cap atop said dielectric cap of said stack.

In some embodiments of this method of the present invention, theantireflective coating (ARC) further includes atoms of X, wherein X isone of O, N, S and F. In another embodiment of the present invention, adielectric cap is formed on top of the substrate prior to forming theARC.

The present invention also contemplates a step of forming contact holesthrough the antireflective coating or material stack including theantireflective coating and the dielectric cap after forming the firstand second interconnect patterns.

In yet other embodiments of the present invention, a curing step isperformed after providing the first interconnect patterns to the firstpatternable low-k material.

In yet a further embodiment of the present invention, the conductivematerial includes Al, Cu, or a Cu alloy. A planarization process such aschemical mechanical polishing may follow the step of filling the firstand second interconnect patterns.

In any of the embodiments mentioned above, the first interconnectpatterns may comprise via openings, while the second interconnectpatterns may comprise line openings. This embodiment is preferred overan embodiment in which the first interconnect patterns comprise lineopenings and the second interconnect patterns comprise via openings.

This invention also relates to a simplified method of fabricatingsingle-damascene low-k interconnect structures with negative-tone orpositive-tone patternable low-k dielectrics. This aspect of the presentinvention comprises the steps of:

providing a patternable low-k material on a surface of an inorganicantireflective coating (ARC) that is located atop a substrate, saidinorganic ARC comprises atoms of M, C and H wherein M is at least one ofSi, Ge, B, Sn, Fe, Ta, Ti, Ni, Hf and La;

forming interconnect patterns within the patternable low-k materialwithout a separate photoresist;

curing the patternable low-k material;

filling said interconnect patterns with a conductive material;

forming a stack comprising a dielectric cap and a block mask locatedatop said cured patternable-low-k dielectric material;

forming at least one airgap through said stack and into at least saidcured patternable low-k dielectric material; and

forming an airgap cap atop said dielectric cap of said stack.

In some embodiments of this method of the present invention, theantireflective coating (ARC) further includes atoms of X, wherein X isone of O, N, S and F. In another embodiment of the present invention, adielectric cap is formed on top of the substrate prior to forming theARC.

The present invention also contemplates a step of forming contact holesthrough the antireflective coating or material stack including theantireflective coating and the dielectric cap after forming theinterconnect patterns.

In yet a further embodiment of the present invention, the conductivematerial is Al, Cu, or a Cu alloy. A planarization process such aschemical mechanical polishing may follow the step of filling theinterconnect patterns.

In any of the embodiments mentioned above, the interconnect patterns maycomprise via openings or line openings.

This patternable low-k/inorganic ARC method of present inventiondramatically reduces the complexity in the fabrication of currentinterconnect structures. The photoresist used in the prior artintegration is no longer needed. In addition to not requiring a separatephotoresist, the present invention also does not utilize a plasmaetching step for patterning as also required in the prior artinterconnect processing schemes. It is further noted that the inventivemethod reduces the number of layers required to fabricate theinterconnect structure and, as such, the present invention reduces thetime and cost of fabricating interconnect structures as compared toprior art processes.

In addition to the methods described above, the present invention alsorelates to airgap-containing interconnect structures which include thepatternable low-k dielectric material in a cured state; in the curedstate the patternable low-k material serves as the interconnectdielectric. In general terms, the present invention provides aninterconnect structure comprising at least one patterned and cured low-kdielectric material located on a surface of a patterned inorganicantireflective coating (ARC) that is located atop a substrate, whereinsaid inorganic ARC comprises atoms of M, C and H wherein M is at leastone of Si, Ge, B, Sn, Fe, Ta, Ti, Ni, Hf and La, said at least one curedand patterned low-k dielectric material and said patterned inorganicantireflective coating having conductively filled regions embeddedtherein and said at least one cured and patterned low-k dielectricmaterial having at least one airgap located adjacent, but not directlyabutting the conductively filled regions.

In some embodiments of the present invention, the antireflective coating(ARC) further includes atoms of X, wherein X is one of O, N, S and F. Insome further embodiments of the present invention, a dual-damasceneinterconnect structure including first and second cured and patternedlow-k materials are provided. In yet another embodiment of the presentinvention, a single-damascene interconnect structure is provided. Insome further embodiments, the patterned low-k materials each have Siatoms bonded to cyclic rings via oxygen atoms.

In a further embodiment of the present invention a patterned dielectriccap layer is located beneath the antireflective coating. In stillanother embodiment of the present invention, another dielectric cap andan airgap cap are present atop the patterned low-k film.

In yet another embodiment of the present invention, the conductivelyfilled regions comprise Al, Cu or a Cu alloy. In an even furtherembodiment of the present invention, the conductively filled regionscomprise a single via, a single line, a combined via/line or a combinedline/via.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1L are pictorial representations (through cross sectionalviews) depicting the basic processing steps employed for fabricating adual-damascene interconnect structure using patternable dielectrics ason-chip electrical insulators on a semiconductor chip in accordance witha highly preferred embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention, which provides airgap-containing low-kinterconnect structures with a combined inorganic antireflective coating(ARC) and a patternable dielectric and methods of fabricating suchinterconnect structures, will now be described in greater detail byreferring to the following discussion and drawings that accompany thepresent application. It is noted that the drawings that accompany thepresent application are provided for illustrative purposes only, and, assuch, these drawings are not drawn to scale.

In the following description, numerous specific details are set forth,such as particular structures, components, materials, dimensions,processing steps and techniques, in order to provide a thoroughunderstanding of the present invention. However, it will be appreciatedby one of ordinary skill in the art that the invention may be practicedwithout these specific details. In other instances, well-knownstructures or processing steps have not been described in detail inorder to avoid obscuring the invention.

It will be understood that when an element as a layer, region orsubstrate is referred to as being “on” or “over” another element, it canbe directly on the other element or intervening elements may also bepresent. In contrast, when an element is referred to as being “directlyon” or “directly over” another element, there are no interveningelements present. It will also be understood that when an element isreferred to as being “connected” or “coupled” to another element, it canbe directly connected or coupled to the other element or interveningelements may be present. In contrast, when an element is referred to asbeing “directly connected” or “directly coupled” to another element,there are no intervening elements present.

As stated above, this invention circumvents the prior art drawbacks ofcurrent integration by combining the functions of a photoresist and adielectric material into one material. This one material, called apatternable low-k dielectric herein, acts as a photoresist during thelithographic patterning process and, as such a separate photoresist isnot required or used in the present invention. After lithographicpatterning, the patternable low-k dielectric is subsequently convertedinto a low-k dielectric during a post patterning cure. In this way, theinventive method avoids plasma etching and the complex sacrificial filmstack and processes required for patterning. Specifically, thisinvention relates to a simplified method of fabricatingairgap-containing low-k interconnect structures with at least onepatternable dielectric.

In general terms, a method is provided that comprises depositing atleast one patternable low-k material on a surface of an inorganicantireflective coating (ARC) that is located atop a substrate, saidinorganic ARC comprises atoms of M, C and H wherein M is at least one ofSi, Ge, B, Sn, Fe, Ta, Ti, Ni, Hf and La; forming at least oneinterconnect pattern within said at least one patternable low-kmaterial, said at least one interconnect pattern is formed withoututilizing a separate photoresist material; curing the at least onepatternable low-k material; filling said at least one interconnectpattern with a conductive material; forming a stack comprising adielectric cap and a block mask located atop said at least one curedpatternable-low-k dielectric material; forming at least one airgapthrough said stack and into said at least one cured patternable low-kdielectric material; and forming an airgap cap atop said dielectric capof said stack.

The inventive method can be used to form dual-damascene interconnectstructures as well as single-damascene interconnect structures.

The present invention will now be described in reference to FIGS. 1A-1Lwhich illustrate a preferred embodiment of the present invention inwhich a dual-damascene interconnect structure including an airgap usingpatternable dielectrics as on-chip electrical insulators on asemiconductor chip is formed.

FIG. 1A illustrates an initial structure 10 that is utilized in thisembodiment of the present invention. The initial structure 10 includes asubstrate 12, an optional dielectric cap 14 located on a surface ofsubstrate 12, and inorganic antireflective coating 16 located on asurface of the optional dielectric cap 14. In the embodiment illustratedherein below, a single airgap is shown. Although a single airgap isshown, the present invention is not limited to interconnect structuresincluding a single airgap. Instead, the present invention contemplatesembodiments in which a plurality of airgaps are formed.

The substrate 12 may comprise a semiconducting material, an insulatingmaterial, a conductive material or any combination thereof (e.g., alower level of an interconnect structure). When the substrate 12 iscomprised of a semiconducting material, any semiconductor such as Si,SiGe, SiGeC, SiC, Ge alloys, GaAs, InAs, InP, other III/V or II/VIcompound semiconductors, and organic semiconductors may be used. Inaddition to these listed types of semiconducting materials, the presentinvention also contemplates cases in which the semiconductor substrateis a layered semiconductor such as, for example, Si/SiGe, Si/SiC,silicon-on-insulators (SOIs) or silicon germanium-on-insulators (SGOIs).

When the substrate 12 is an insulating material, the insulating materialcan be an organic insulator, an inorganic insulator or a combinationthereof including multilayers. The substrate 12 may also include apatternable low-k dielectric material of this invention as well. Whenthe substrate 12 is a conducting material, the substrate may include,for example, polySi, an elemental metal, alloys of elemental metals, ametal silicide, a metal nitride, conductive nanotubes and nanowires orcombinations thereof including multilayers. When the substrate 12comprises a semiconducting material, one or more semiconductor devicessuch as, for example, complementary metal oxide semiconductor (CMOS)devices can be fabricated thereon.

The optional dielectric cap 14 is formed on the surface of substrate 12utilizing a conventional deposition process such as, for example,chemical vapor deposition (CVD), plasma enhanced chemical vapordeposition (PECVD), atomic layer deposition (ALD), spin coating, brushcoating, spray coating, dip coating, or evaporation. The dielectric cap14 comprises any suitable dielectric capping material such as, forexample, SiC, SiN, SiO₂, a carbon doped oxide, a nitrogen and hydrogendoped silicon carbide SiC(N,H) or multilayers thereof. This dielectriccap can be a continuous layer or a discontinuous layer. It can also be aselect cap, such as CoWP. The thickness of the dielectric cap 14 mayvary depending on the technique used to form the same as well as thematerial make-up of the layer. Typically, the dielectric cap 14 has athickness from about 15 to about 55 nm, with a thickness from about 25to about 45 nm being more typical.

Next, an inorganic antireflective coating (ARC) 16 is formed on asurface of the optional dielectric cap 14 if present, or directly on asurface of the substrate 12 when the dielectric cap 14 is not present.The ARC 16 may be designed to control reflection of light that istransmitted through the patternable low-k film (to be subsequentlyformed), reflected off the substrate and back into the patternable low-kfilm, where it can interfere with incoming light and cause thepatternable low-k film to be unevenly exposed. The ARC's opticalconstants are defined here as the index of refraction n and theextinction coefficient k. In general, ARC 16 can be modeled so as tofind optimum optical parameters (n and k values) of ARC as well asoptimum thickness. The preferred optical constants of the ARC 16 are inthe range from about n=1.4 to n=2.6 and k=0.01 to k=0.78 at a wavelengthof 248, 193 and 157, 126 nm and extreme ultraviolet (13.4 nm) radiation.

The optical properties and thickness of ARC 16 is optimized to obtainoptimal resolution and profile control of the patternable low-k materialduring the subsequent patterning steps, which is well known to thoseordinarily skilled in the art. The thickness of the ARC 16 may varydepending on the technique used to form the same as well as the materialmake-up of the layer. Typically, the ARC 16 has a thickness from about 5to about 200 nm, with a thickness from about 20 to about 140 nm beingmore typical.

The ARC 16 of the present invention is a composition that includes atomsof M, C and H, wherein M is at least one of Si, Ge, B, Sn, Fe, Ta, Ti,Ni, Hf and La. The inorganic ARC may optionally include atoms of O, N,S, F or mixtures thereof. In some embodiments, M is preferably Si. Insome embodiments, the ARC composition may also be referred to as a vapordeposited M:C:H:optionally X material, wherein M and X are as definedabove.

The ARC 16 is produced by a vapor or liquid phase deposition (such as,for example, CVD, PECVD PVD, ALD and spin-on coating) method usingappropriate Si, Ge, B, Sn, Fe, Ta, Ti, Ni, Hf and La precursors byadjusting process parameters and/or precursor composition. In the caseof Si:C:H:X films, these are deposited from methylsilanes with/withoutadditions of nitrogen and/or oxygen and/or fluorine and/or sulfurcontaining precursors.

Other precursors are also contemplated in the present invention besidesmethylsilanes. Typically, any precursor including M, C and H can be usedin the present invention. That is, any precursor including M and atleast one organic ligand can be used. Examples include methylsilanessuch as trimethylsilane or tetramethylsilane, siloxanes such astetramethylcylcotetrasiloxane or octylmethylcyclotetrasiloxane, ormethyl gemanes such as trimethylgermane or tetraethylgermane.

Other organic precursors may also be used in the present invention, inaddition to the organometallic ones, to tune optical, electrical,mechanical properties of the ARC 16 and/or the film stack. These organicprecursors are selected from hydrocarbon and its derivatives, includinglinear, branched, and ring type molecules.

The atomic % ranges for M are the following: preferably about 0.1 atomic% to about 95 atomic %, more preferably about 0.5 atomic % to about 95atomic %, most preferably about 1 atomic % to about 60 atomic % and mosthighly preferably about 5 atomic % to about 50 atomic %.

The atomic % ranges for C are the following: preferably about 0.1 atomic% to about 95 atomic %, more preferably about 0.5 atomic % to about 95atomic %, most preferably about 1 atomic % to 60 atomic % and mosthighly preferably about 5 atomic % to 50 atomic %.

The atomic % ranges for H are the following: preferably about 0.1 atomic% to about 50 atomic %, more preferably about 0.5 atomic % to about 50atomic %, most preferably about 1 atomic % to about 40 atomic % and mosthighly preferably about 5 atomic % to about 30 atomic %.

The atomic % ranges for X are the following: preferably O atomic % toabout 70 atomic %, more preferably about 0.5 atomic % to about 70 atomic%, most preferably about 1 atomic % to about 40 atomic % and most highlypreferably about 5 atomic % to about 30 atomic %.

The ARC 16 produced by the present invention has a tunable index ofrefraction and extinction coefficient which can be optionally gradedalong the film thickness to match the optical properties of thesubstrate and the patternable low-k material. The optical properties atDUV and the lithographic features of the ARC produced by the presentinvention are vastly superior to those obtained by other hardmaskmaterials such as oxide type materials (TEOS, BSG) and nitride typematerials.

In one preferred embodiment, the ARC 16 of the present invention isformed by plasma enhanced chemical vapor deposition (PECVD) techniques.In one type of technique, the PECVD process is performed in a parallelplate reactor where the substrate is placed on one of the electrodes.

The following are a list of non-limiting exemplary embodiments in whichthe ARC is deposited on a substrate that is positioned on a poweredelectrode and therefore a negative bias is required:

In one embodiment, a Si:C:H film is deposited under the followingconditions: precursor=tetramethylsilane at a flow of 10 sccm, pressurein reactor=200 mtorr, substrate temperature=60° C., substrate bias=−200V.

In a second embodiment, a Si:C:O:H film is deposited under the followingconditions: precursor=tetramethylsilane at a flow of 10 sccm mixed withoxygen at a flow of 2 sccm, pressure in reactor=200 mtorr, substratetemperature=180° C., substrate bias=−200 V.

In a third embodiment, a Si:C:H film is deposited under the followingconditions: precursor=trimethylsilane at a flow of 10 sccm, pressure inreactor=200 mtorr, substrate temperature=60° C., substrate bias=−200 V.

In a fourth embodiment, a Si:C:O:H film is deposited under the followingconditions: precursor=trimethylsilane at a flow of 10 sccm mixed withoxygen at a flow of 2 sccm, pressure in reactor=200 mtorr, substratetemperature=60° C., substrate bias=−200 V.

In a fifth embodiment, a Si:C:O:H film is deposited under the followingconditions: precursor=tetramethyltetrasiloxane with argon as a carriergas at flow of 30 sccm, pressure in reactor=250 mtorr, substratetemperature=60° C., substrate bias=−150 V.

In a sixth embodiment, a Si:C:O:H film is deposited under the followingconditions: precursor=tetramethyltetrasiloxane with argon as a carriergas at flow of 30 sccm, pressure in reactor=250 mtorr, substratetemperature=180° C., substrate bias=−200 V.

In a seventh embodiment, a Si:C:O:H film is deposited under thefollowing conditions: precursor=tetramethyltetrasiloxane with argon as acarrier gas at flow of 30 sccm, pressure in reactor=200 mtorr, substratetemperature=180°, substrate bias=−200 V.

In an eighth embodiment, a Ge:C:H film is deposited under the followingconditions: precursor=tetramethylgermane with argon as a carrier gas atflow of 30 sccm, pressure in reactor=50 mtorr, substratetemperature=180° C., substrate bias=−250 V.

In a ninth embodiment, a Ge:C:H film is deposited under the followingconditions: precursor=tetramethylgermane with argon as a carrier gas atflow of 30 sccm, pressure in reactor=100 mtorr, substratetemperature=60° C., substrate bias=−50 V.

In a tenth embodiment, a Ge:C:H:O film is deposited under the followingconditions: precursor=tetramethylgermane at a flow of 15 sccm mixed withoxygen at a flow of 2 sccm, pressure in reactor=200 mtorr, substratetemperature=60° C., substrate bias=−50 V.

The ARC 16 can be deposited also in a parallel plate PECVD reactor withthe substrate positioned on the grounded electrode. It can be depositedin conditions similar to those described in the previous examples but atsubstrate temperatures up to 400° C., and in high-density plasma typereactors under suitable chosen conditions.

It should be noted that by changing process parameters such as biasvoltage, gas mixture, gas flow, pressure and deposition temperature, thefilm optical constants can be changed. In addition, the composition ofthe starting precursor as well as the introduction of oxygen, nitrogen,fluorine, and sulfur containing precursors also allows the tunability ofthese films. The ARC's optical constants are defined here as the indexof refraction n and the extinction coefficient k. In general, ARC 16 canbe modeled so as to find optimum optical parameters (n and k values) ofARC as well as optimum thickness. The preferred optical constants of theARC 16 are in the range from about n=1.4 to n=2.6 and k=0.01 to k=0.78at a wavelength of 248, 193 and 157 nm, 126 nm and extreme ultravioletradiation.

In addition to the above, the ARC 16 does not interact with thepatternable low-k material to induce residue, footing or undercutting.

Moreover, the ARC 16 has good etch selectivity to the patternabledielectric material. Etch selectivities of 1.5-4 to 1 of the ARC topatternable low-k material may be obtained.

Furthermore, the use of the ARC 16 of the present invention maintainsthe pattern integrity after curing of the patternable low-k material.

Next, and as illustrated in FIG. 1B, a first patternable low-k material18, which combines the function of a photoresist and low-k dielectricinto one single material is provided. As shown, the first patternablelow-k material 18 is provided directly on the surface of the ARC 16.

The first patternable low-k material 18 is provided (i.e., formed)utilizing a conventional deposition process including, for example,spin-on-coating, spray coating, dip coating, brush coating, andevaporation. After applying the first patternable low-k material 18, apost deposition baking step is typically, but not necessarily always,required to remove unwanted components, such as solvent. When performed,the baking step is conducted at a temperature from about 60° to about200° C., with a baking temperature from about 80° to about 140° C. beingeven more preferred. The duration of the baking step varies and is notcritical to the practice of the present invention.

The thickness of the first patternable low-k material 18 may varydepending on the technique used to form the same as well as the materialmake-up of the layer. Typically, the first patternable low-k material 18has a thickness from about 10 to about 10000 nm, with a thickness fromabout 50 to about 2000 nm being more typical.

As stated above, the first patternable low-k material 18 functions as aphotoresist and is converted into a low-k dielectric during postpatterning processing, by heat, UV light, electron beam, ion beam,microwave, plasma cure, or combinations thereof. For instance, the firstpatternable low-k material 18 may comprise a functionalized polymerhaving one or more acid-sensitive imageable groups. These polymers orblends of polymers can be converted into low-k dielectrics aftersubsequent processing.

More specifically, the first patternable low-k material 18 comprisesphoto/acid-sensitive polymers of hydrocarbons, fluorinated hydrocarbons,siloxane, silane, carbosilane, oxycarbosilane, organosilicates,silsesquioxanes and the like. The polymers include, for example,silsesquioxane-type polymers including caged, linear, branched orcombinations thereof. In one embodiment, the first patternabledielectric material 18 comprises a blend of these photo/acid-sensitivepolymers. The first patternable dielectric material 18 may furthercomprise at least one sacrificial pore generator to reduce thedielectric constant in its cured form. Examples of patternabledielectric materials useable with the present disclosure are disclosedin U.S. Pat. Nos. 7,041,748, 7,056,840, and 6,087,064, all of which areincorporated herein by reference in their entirety. The dielectricconstant of the patternable low-k material 18 after cure is generally nomore than 4.3. The dielectric constant may be greater than 1 and up toabout 4.3, more preferably from about 1 to about 3.6, even morepreferably from about 1 to about 3.0, further more preferably from about1 to about 2.5, with from about 1 to about 2.0 being most preferred.

The first patternable low-k material 18 is formed from a compositionthat includes one of the above mentioned polymers or polymer blends, aphotoacid generator, a base additive and a solvent typically used in aphotoresist. The photoacid generators, base additives and solvents arewell known to those skilled in the art and, as such, details regardingthose components are not fully provided.

In a preferred embodiment, the first patternable low-k material 18 is anegative patternable low-k material comprising a silsesquioxane polymeror copolymer including, for example, poly(methylsilsesquioxane) (PMS),poly(p-hydroxybenzylsilsesquioxane) (PHBS),poly(p-hydroxyphenylethylsilsesquioxane) (PHPES),poly(p-hydroxyphenylethylsilsesquioxane-co-p-hydroxy-alpha-methylbenzylsilsesquioxane) (PHPE/HMBS),poly(p-hydroxyphenylethylsilsesquioxane-co-methoxybenzylsilsesquioxane)(PHPE/MBS),poly(p-hydroxyphenylethylsilsesquioxane-co-t-butylsilsesquioxane)(PHPE/BS),poly(p-hydroxyphenylethylsilsesquioxane-co-cyclohexylsilsesquioxane)(PHPE/CHS),poly(p-hydroxyphenylethylsilsesquioxane-co-phenylsilsesquioxane)(PHPE/PS),poly(p-hydroxyphenylethylsilsesquioxane-co-bicycloheptylsilsesquioxane)(PHPE/BHS), polyp-hydroxy-alpha-methylbenzylsilsesquioxane) (PHMBS),polyp-hydroxy-alpha-methylbenzylsilsesquioxane-co-p-hydroxybenzylsilsesquioxane)(PHMB/HBS),poly(p-hydroxy-alpha-methylbenzylsilsesquioxane-co-methoxybenzylsilsesquioxane)(PHMB/MBS),poly(p-hydroxy-alpha-methylbenzylsilsesquioxane-co-t-butylsilsesquioxane)(PHMB/BS),poly(p-hydroxy-alpha-methylbenzylsilsesquioxane-co-cyclohexylsilsesquioxane)(PHMB/CHS),poly(p-hydroxy-alpha-methylbenzylsilsesquioxane-co-phenylsilsesquioxane)(PHMB/PS),poly(p-hydroxy-alpha-methylbenzylsilsesquioxane-co-bicycloheptylsilsesquioxane)(PHMB/BHS),poly(p-hydroxybenzylsilsesquioxane-co-p-hydroxyphenylethylsilsesquioxane)(PHB/HPES), andpoly(p-hydroxy-alpha-methylbenzylsilsesquioxane-co-p-alpha-methylbenzylsilsesquioxane)(PHMB/MBS).

In the compositions containing a blended polymer component, thesilsesquioxane polymer in the blend may be selected from thesilsesquioxane polymers described above or may be selected from othersilsesquioxane polymers such as, for example,poly(methyl-silsesquioxane) (PMS), poly(p-hydroxybenzylsilsesquioxane)(PHBS),poly(p-hydroxybenzylsilsesquioxane-co-methoxybenzylsilsesquioxane)(PHB/MBS),poly(p-hydroxy-alpha-methylbenzylsilsesquioxane-co-p-alpha-methylbenzylsilsesquioxane)(PHMB/MBS), poly(p-hydroxybenzylsilsesquioxane-co-t-butylsilsesquioxane)(PHB/BS),poly(p-hydroxybenzylsilsesquioxane-co-cyclohexylsilsesquioxane)(PHB/CHS), poly(p-hydrooxybenzylsilsesquioxane-co-phenylsilsesquioxane)(PHB/PS),poly(p-hydroxybenzylsilsesquioxane-co-bicycloheptylsilsesquioxane)(PHB/BHS), and caged silsesquioxanes such asoctakis(glycidyloxypropyl)dimethylsilyloxy)silsesquioxane,octakis[cyclohexenyl epoxide)dimethylsilyloxy]silsesquioxane,octakis[4-(hydroxyphenylethyl)dimethylsilyloxy]silsesquioxane, andoctakis[{2-(1′,1′-bis(trifluoromethyl)-1′-hydroxyethyl)norbornyl}dimethylsilyloxy]silsesquioxane.If desired, a combination of different silsesquioxane polymers may beused in the blend with the non-silsesquioxane polymer.

For positive tone patternable low-k material, the silicon-containingpolymer employed in the present invention may be a homopolymer or acopolymer. Suitable types of such silicon-containing polymers includehomopolymers or copolymers containing at least one monomer selected fromthe group consisting of a siloxane, a silane, a silsesquioxane and asilyne. Highly preferred silicon-backbone polymers are selected from thegroup consisting of poly(hydroxyphenyl alkyl)silsesquioxanes andpoly(hydroxyphenyl alkyl) siloxanes, wherein the alkyl is a C₁₋₃₀moiety. These preferred silicon-containing polymers are preferably fullyor partially protected with acid-sensitive protecting groups.

The positive-tone patternable low-k material may comprise blends of anon-silicon containing polymer and a silicon-containing polymericadditive with a silicon-containing substituent bonded to the polymericbackbone, the silicon-containing polymeric additive may be a homopolymeror copolymer containing at least one monomer having a silicon-containingsubstituent. The silicon-containing substituent may or may not be acidsensitive. Typically, however the substituent is acid sensitive whencontaining a C₂ alkyl moiety. Preferably, the silicon-containingsubstituent is attached to a monomer selected from the group consistingof hydroxystyrene, an acrylate, a methacrylate, an acrylamide, amethacrylamide, itaconate, an itaconic half ester or a cycloolefin.Preferred silicon-containing substituents include: siloxane, silane andcubic silsesquioxanes. The silicon-containing polymer may furtherinclude silicon-free monomers such as those selected from the groupconsisting of styrene, hydroxystyrene, acrylic acid, methacrylic acid,itaconic acid and an anhydride such as maleic anhydride and itaconicanhydride.

Preferred monomers containing silicon-containing substituents aretrimethylsilyl alkyl acrylate, trimethylsilyl alkyl methacrylate,trimethylsilyl alkyl itaconate, tris(trimethylsilyl)silyl alkyl acrylatetris(trimethylsilyl)silyl alkyl methacrylate, tris(trimethylsilyl)silylalkyl itaconate, tris(trimethylsilyloxy)silyl alkyl acrylate,tris(trimethylsilyloxy)silyl alkyl methacrylate,tris(trimethylsilyloxy)silyl alkyl itaconate, alkylsilyl styrene,trimethylsilylmethyl(dimethoxy)silyloxy alkyl acrylate,trimethylsilylmethyl(dimethoxy)silyloxy alkyl methacrylate,trimethylsilylmethyl(dimethoxy)silyloxy alkyl itaconate, trimethylsilylalkyl norbornene-5-carboxylate alkyl, tris(trimethylsilyl)silyl alkylnorbornene-5-carboxylate and tris(trimethylsilyloxy)silyl alkylnorbornene-5-carboxylate, wherein alkyl is a C₁₋₅ moiety.

Highly preferred species of these monomers are3-(3,5,7,9,11,13,15-heptacyclopentylpentacyclo[9.5.1.13,9.15,15.17,13]-octasiloxan-1-yl)propylmethacrylate,1,3,5,7,9,11,13-heptacyclopentyl-15-vinylpentacyclo[9.5.1.13,9.15,15.17,13]octasiloxane,methacrylamidotrimethylsilane,O-(methacryloxyethyl)-N-(triethoxysilylpropyl)urethane,methacryloxyethoxytrimethylsilane,N-(3-methacryloxy-2-hydroxypropyl)-3-aminopropyltriethoxysilane,(methacryloxymethyl)bis(trimethylsiloxy)methylsilane,(m,p-vinylbenzyloxy)trimethylsilane,methacryloxypropyltris(trimethylsiloxy)silane,methacryloxytrimethylsilane,3-methacryloxypropylbis(trimethylsiloxy)methylsilane,3-methacryloxypropyldimethylchlorosilane,methacryloxypropyldimethylethoxysilane,methacryloxypropyldimethylmethoxysilane,methacryloxypropylheptacyclopentyl-T8-silsequioxane,methacryloxypropylmethyldichlorosilane,methacryloxypropylmethyldiethoxysilane,methacryloxypropylmethyldimethoxysilane,(methacryloxymethyl)dimethylethoxysilane,(methacryloxymethyl)phenyldimethylsilane(phenyldimethylsilyl)methylmethacrylate,methacryloxymethyltriethoxysilane, methacryloxymethyltrimethoxysilane,methacryloxymethyltris(trimethylsiloxy)silane,O-methacryloxy(polyethyleneoxy)trimethylsilane,methacryloxypropylpentamethyldisiloxane, methacryloxypropylsilatrane,methacryloxypropylsiloxane macromer, methacryloxypropyl terminatedpolydimethylsiloxane, methacryloxypropyltrichlorosilane,methacryloxypropyltriethoxysilane, methacryloxypropyltrimethoxysilane,methacryloxypropyltris(methoxyethoxy)silane,p-(t-butyldimethylsiloxy)styrene, butenyltriethoxysilane,3-butenyltrimethylsilane, (3-acryloxypropyl)trimethoxysilane,(3-acryloxypropyl)tris(trimethylsiloxy)silane,O-(trimethylsilyl)acrylate, 2-trimethylsiloxyethlacrylate,N-(3-acryloxy-2-hydroxypropyl)-3-aminopropyltriethoxysilane,(3-acryloxypropyl)dimethylmethoxysilane,(3-acryloxypropyl)methylbis(trimethylsiloxy)silane,(3-acryloxypropyl)methyldichlorosilane, and(3-acryloxypropyl)methyldimethoxysilane,(3-acryloxypropyl)trichlorosilane.

The extent of protection and the amount of co-monomer present in thesilicon containing polymeric additive are such that the patternablelow-k material will provide good lithography performance, i.e., highresolution and a good process window. Examples of protecting groupswhich can be employed are cyclic and branched (secondary and tertiary)aliphatic carbonyls, esters or ethers containing from 3 to 30 carbonatoms, acetals, ketals and aliphatic silylethers.

Examples of cyclic or branched aliphatic carbonyls that may be employedin the present invention include, but are not limited to: phenoliccarbonates; t-alkoxycarbonyloxys such as t-butoxylcarbonyloxy andisopropyloxycarbonyloxy. A highly preferred carbonate ist-butoxylcarbonyloxy.

Some examples of cyclic and branched ethers that may be employed in thepresent invention include, but are not limited to: benzyl ether andt-alkyl ethers such t-butyl ether. Of the aforesaid ethers, it is highlypreferred to use t-butyl ether.

Examples of cyclic and branched esters that can be employed in thepresent invention are carboxylic esters having a cyclic or branchedaliphatic substituent such as t-butyl ester, isobornyl ester,2-methyl-2-admantyl ester, benzyl ester, 3-oxocyclohexanyl ester,dimethylpropylmethyl ester, mevalonic lactonyl ester,3-hydroxy-g-butyrolactonyl ester, 3-methyl-g-butylrolactonyl ester,bis(trimethylsilyl)isopropyl ester, trimethylsilylethyl ester,tris(trimethylsilyl)silylethyl ester and cumyl ester.

Some examples of acetals and ketals that can be employed in the presentinvention include, but are not limited to: phenolic acetals and ketalsas well as tetrahydrofuranyl, tetrahydropyranyl, 2-ethoxyethyl,methoxycyclohexanyl, methoxycyclopentanyl, cyclohexanyloxyethyl,ethoxycyclopentanyl, ethoxycyclohexanyl, methoxycycloheptanyl andethoxycycloheptanyl. Of these, it is preferred that amethoxycyclohexanyl ketal be employed.

Illustrative examples of silylethers that can be employed in the presentinvention include, but are not limited to: trimethylsilylether,dimethylethylsilylether and dimethylpropylsilylether. Of thesesilylethers, it is preferred that trimethylsilylether be employed.

In a preferred embodiment for negative-tone patternable low-k materialsof the present invention are two miscible, or compatible,silsesquioxanes. The first silsesquioxane polymer is a linear, branched,caged compound or combination thereof having the following structuralformula:

wherein each occurrence of R₁ is one or more acidic functional groupsfor base solubility; each occurrence of R₂ is a carbon functionality forcontrolling polymer dissolution in an aqueous base; R₁ is not equal toR₂; m and n represent the number of repeating units; m is an integer;and n is zero or an integer greater than zero.

In the present invention, R₁ is not limited to any specific functionalgroup, and is preferably selected from among linear or branched alkylswhich are substituted with OH, C(O)OH, and/or F; cycloalkyls which aresubstituted with OH, C(O)OH, and/or F; aromatics which are substitutedwith OH, C(O)OH, and/or F; arenes that are substituted with OH, C(O)OH,and/or F; and acrylics which are substituted with OH, C(O)OH, and/or F.Examples of preferred R₁ include:

In the present invention, R₂ is not limited to any specific carbonfunctional group, and is preferably selected from among linear orbranched alkyls, cycloalkyls, aromatics, arenes, and acrylates.

The silsesquioxane polymers of the present invention have a weightaveraged molecular weight of about 400 to about 500,000, and morepreferable from about 1500 to about 10,000. The R₁ and R₂ proportionsand structures are selected to provide a material suitable forphotolithographic processes and maintaining pattern fidelity after postpatterning cure.

A second polymer component of the blend material includes but is notlimited to a family of organosilicates known as silsesquioxanes, havingthe structural formula:

wherein R₃ is preferable selected from alkyls, cycloalkyls, aryl, or acombination thereof, and are commercially available from Dow Corning,Shin-Etsu, or JSR, for example. The silsesquioxane is preferablypoly(methylsilsesquioxane), and n is an integer about 10 to about 1,000or more (including copolymers). The silsesquioxane polymers possesssilanol end groups, but may also include halosilanes, acetoxysilanes,silylamines, and alkoxysilanes. In a preferred embodiment of the presentinvention, silsesquioxane polymers, LKD-2021, LKD-2056 and LKD-2064 andthe like (from JSR Corporation) which contain silanol end groups areemployed.

The composition of the silsesquioxane polymers in the blend formulationis 1 to 99% of the total polymer composition. In the preferredembodiment of the invention, the composition of the acid sensitivepolymer is 20 to 80% of the total polymer composition, and even morepreferred, 30 to 60%.

A third component of the patternable low-k composition of the presentinvention is a pore-generating compound, called a porogen. The porogenprovides nanoscopic pores in the composition of matter of the presentinvention which further reduces the dielectric constant of the material.

The porogen that can be used in the present invention includes miscibleor phase separated, i.e., non-miscible, polymers that are capable ofdecomposing under heat or radiation. Alternatively, the porogen may beextracted with supercritical fluid techniques. Examples of porogens thatmay be employed in the present invention include: homopolymers,copolymers, organic nanoscopic polymers, thermoplatic polymers,star-shaped polymers, dendrimers or crosslinked polymers that remainsubstantially dormant during the patterning process. After patterning,the pore generating polymers are decomposed or extracted to enhance thedielectric properties of the material of the present invention withoutseverely degrading the pattern fidelity. The decomposition of theporogen may be by heat or radiation-induced.

When a porogen is employed, it is present in the composition of thepresent invention in an amount of from about 0.1 to about 99.9% of thefunctionalized polymer. More preferably, the porogen is present in anamount of from about 5 to about 90% of the functionalized polymer.

A fourth component of the present invention is a photosensitive acidgenerator (PAG) that is compatible with the other components. Examplesof preferred PAGs include:-(trifluoro-methylsulfonyloxy)-bicyclo[2.2.1]hept-5-ene-2,3-dicarboximide(MDT), onium salts, aromatic diazonium salts, sulfonium salts,diaryliodonium salts, and sulfonic acid esters of N-hydroxyamides or-imides, as disclosed in U.S. Pat. No. 4,371,605. The content of the'605 patent is incorporated herein by reference. A weaker acid generatedfrom a PAG such as N-hydroxy-naphthalimide (DDSN) may be used.Combinations of PAGs may be used.

Condensation in the presence of an acid generated by a photoacidgenerator under exposure to radiation is not limited to silanols, butmay also include halosilanes, acetoxysilanes, silylamines, andalkoxysilanes. Organic crosslinking agents, such asmethylphenyltetramethoxymethyl glycouril (methylphenyl powderlink), mayalso be included in the formulation. Although photoacid generators arepreferred for crosslinking, photobase generators can also be used forcrosslinking silanol polymers.

The patternable low-k material of the present invention also includes acasting solvent to dissolve the other components. Examples of suitablecasting solvent include and are not limited to ethoxyethylpropionate(EEP), a combination of EEP and γ-butyrolactone, propylene-glycolmonomethylether alcohol and acetate, propyleneglycol monopropyl alcoholand acetate, and ethyl lactate. Combinations of these solvents may alsobe used.

In optimizing the photolithography process, an organic base may be addedto the formulation. The base employed in the present invention may beany suitable base known in the resist art. Examples of bases includetetraalkylammonium hydroxides, cetyltrimethylammonium hydroxide, and1,8-diaminonaphthalene. The compositions of the present invention arenot limited to any specific selection of base.

The term “acid-sensitive” is used throughout the application to denoteimageable functional groups which undergo a chemical reaction in thepresence of an acid generated by a photoacid generator under exposure toradiation. The acid-sensitive imageable functional groups employed inthe present invention may include acid-sensitive positive-tonefunctional groups or acid-sensitive negative-tone functional groups. Thenegative-tone acid-sensitive functional groups are functional groups forcausing a crosslinking reaction which causes the exposed areas to beinsoluble in a developer to form a negative-tone relief image afterdevelopment. The positive-tone acid-sensitive functional groups areacid-sensitive protecting groups which cause the exposed region to besoluble in a developer to form positive-tone relief images afterdevelopment.

The aforementioned patternable low-k materials act as photoresists usingpatterning; they can be positive-tone or negative-tone, and sensitive toG-line, Mine, DUV (248 nm, 193 nm, 157 nm, 126 nm, and EUV (13.4 μm).

Next, and as shown in FIG. 1C, the first patternable low-k dielectricmaterial 18 is pattern-wise exposed to form latent images of a desiredcircuitry. An optional post-exposure baking may be required to effectthe photochemical reactions. When performed, the baking step isconducted at a temperature from about 60° to about 200° C., with abaking temperature from about 80° to about 140° C. being even morepreferred. The duration of the baking step varies and is not critical tothe practice of the present invention. After exposure and post-exposurebaking, the latent images are developed into the low-k material with anappropriate developer, usually an aqueous base solution, such as 0.26Ntetramethylammoniahydroxide (TMAH) solution.

The pattern-wise exposing process can be accomplished in a variety ofways, including, for example, through a mask with a lithography stepperor a scanner with an exposure light source of G-line, Mine (365 nm), DUV(248 nm, 193 nm, 157 nm, 126 nm), Extreme UV (13.4 nm), or an electronbeam, an ion beam. The pattern-wise exposing process also includesdirect writing without the use of a mask with, for example, light,electron beam, ion beam, and scanning probe lithography. Otherpatterning techniques that can be used in the present invention includecontact printing techniques such as nanoimprint lithography, embroising,micro contact printing, replica molding, microtransfer molding,micromolding in capillaries and solvent-assisted micromolding, thermalassisted embroising, inject printing, and the like.

Specifically, FIG. 1C illustrates the structure that is formed afterforming first interconnect patterns 20 within the patternable low-k film18. The first interconnect patterns 20 may include at least one viaopening (as shown and as preferred) or at least one line opening (notshown and less preferred than forming a via opening at this stage of theinventive method). As shown, the first interconnect patterns expose asurface of the ARC 16.

After forming the first interconnect patterns, the low-k material 18 istypically, but not necessarily always, cured to form a cured low-kmaterial 18′ (See, FIG. 1C) in which the cured low-k material typicallyhas Si atoms that are bonded to cyclic rings (aliphatic or aromatic)through oxygen atoms. This type of bonding is evident from C¹³NMR or²⁹Si NMR. The curing is optional when the first patternable low-kmaterial is negative-tone, but it is required when the first patternablelow-k material is a positive-tone material.

Curing is performed in the present invention by a thermal cure, anelectron beam cure, an ultra-violet (UV) cure, an ion beam cure, aplasma cure, a microwave cure or a combination thereof. The conditionsfor each of the curing processes are well known to those skilled in theart and any condition can be chosen as long as it coverts thepatternable low-k material into a low-k film and maintains patternfidelity.

In another embodiment, the irradiation cure step is performed by acombination of a thermal cure and an ultra-violet (UV) cure wherein thewavelength of the ultra-violet (UV) light is from about 50 to about 300nm and the light source for the ultra-violet (UV) cure is a UV lamp, anexcimer (exciplex) laser or a combination thereof.

The excimer laser may be generated from at least one of the excimersselected from the group consisting of Ar₂*, Kr₂*, F₂, Xe₂*, ArF, KrF,XeBr, XeCl, XeCl, XeF, CaF₂, KrCl, and Cl₂ wherein the wavelength of theexcimer laser is in the range from about 50 to about 300 nm.Additionally, the light of the ultra-violet (UV) cure may be enhancedand/or diffused with a lens or other optical diffusing device known tothose skilled in the art.

In one embodiment, this post patterning cure is a combined UV/thermalcure. This combined UV/thermal cure is carried on a UV/thermal curemodule under vacuum or inert atmosphere, such as N₂, He, Ar. Typically,the UV/thermal cure temperature is from about 100° C. to about 500° C.,with a cure temperature from about 300° to about 450° C. being moretypical. The duration of the UV/thermal cure is from about 0.5 min toabout 30 min with a duration from about 1 to about 10 min being moretypical. The UV cure module is designed to have a very low oxygencontent to avoid degradation of the resultant dielectric materials.

After patterning and optionally curing the first patternable low-kmaterial 18, a second patternable low-k material 22 is then formedproviding the structure shown in FIG. 1D. The second patternable low-kmaterial 22 may comprise the same or different material as the firstpatternable low-k material 18. The deposition processes and thicknessmentioned above for the first patternable low-k material 18 are eachapplicable here for the second patternable low-k material 22. Typically,and in the embodiment illustrated, the first patternable low-k material18 or the second low-k material 22 is either a negative-tone or apositive-tone material.

Next, and as shown in FIG. 1E, the second patternable low-k dielectricmaterial 22 is patterned to include second interconnect patterns 24. Thepatterning of the second patternable low-dielectric material 22 isperformed utilizing the same basic processing equipment and steps asthose used for patterning the first patternable low-k dielectricmaterial. In the illustrated embodiment, the second interconnect patternis typically a line. The second interconnect pattern may also be a via,when the first interconnect pattern is a line.

After patterning the second patternable low-k material 22, the structureis cured providing the structure shown in FIG. 1F. In FIG. 1F, referencenumeral 22′ denotes the cured second low-k material Like the first curedlow-k material 18′, the cured second low-k material 22′ has a dielectricconstant within the ranges mentioned above and it also is characterizedas typically having Si atoms bonding to cyclic rings (aliphatic oraromatic) via oxygen atoms. If not previously cured, this curing stepalso cures the first patternable low-k material 18 into a cured low-kmaterial 18′ having the bonding mentioned above. The cure methods,equipment and processes mentioned above for the first patternable low-kmaterial 18 are each applicable here for the second patternable low-kmaterial 22.

At this point of the present invention, and as is shown in FIG. 1F, anetching step is performed that etches through the ARC 16 and dielectriccap 14 if present. The etching step to ‘open’ the ARC 16 and theoptional dielectric cap 14 includes any etching process such as, forexample, reactive ion etching or gas cluster ion beam etching.

Next, a diffusion barrier liner (not shown), which may comprise Ta, TaN,Ti, TiN, Ru, RuTaN, RuTa, W, WN or any other material that can serve asa barrier to prevent conductive material from diffusing there through,is typically formed into the first and second interconnect patterns by adeposition process such as, for example, atomic layer deposition (ALD),chemical vapor deposition (CVD), plasma enhanced chemical vapordeposition (PECVD), physical vapor deposition (PVD), sputtering,chemical solution deposition, or plating. In some embodiments (notshown), the diffusion barrier liner may comprise a combination oflayers. The thickness of the diffusion barrier liner may vary dependingon the exact means of the deposition process employed as well as thematerial and number of layers employed. Typically, the diffusion barrierliner has a thickness from about 4 to about 40 nm, with a thickness fromabout 7 to about 20 nm being more typical.

Following the formation of the diffusion barrier liner, the remainingregion of the first and second interconnect patterns is filled with aconductive material 26 forming a conductive feature. The conductivematerial 26 used in forming the conductive feature includes, forexample, polySi, a conductive metal, an alloy comprising at least oneconductive metal, a conductive metal silicide, a conductive nanotube ornanowire or combinations thereof. Preferably, the conductive material 26that is used in forming the conductive feature is a conductive metalsuch as Cu, W or Al, with Cu or a Cu alloy (such as AlCu) being highlypreferred in the present invention. The conductive material 26 is filledinto the remaining first and second interconnect patterns utilizing aconventional deposition process including, but not limited to CVD,PECVD, sputtering, chemical solution deposition or plating.

After deposition, a conventional planarization process such as, forexample, chemical mechanical polishing (CMP) can be used to provide astructure in which the diffusion barrier liner and the conductivematerial 26 each have an upper surface that is substantially coplanarwith the upper surface of the cured second low-k material 22′. Theresultant structure after filling the openings in the first and secondlow-k patternable materials and planarization is shown, for example, inFIG. 1G.

After forming the at least one conductive material 26 a stack 28including another dielectric cap 30 and a block mask 32 is typicallyformed on the surface of the cured second low-k material 22′. Thestructure including stack 28 is shown in FIG. 1H. The dielectric cap 30of stack 28 is formed utilizing a conventional deposition process suchas, for example, CVD, PECVD, chemical solution deposition, orevaporation. The dielectric cap 30 of stack 28 comprises any suitabledielectric capping material such as, for example, SiC, SiN, SiO₂, acarbon doped oxide, a nitrogen and hydrogen doped silicon carbideSiC(N,H) or multilayers thereof. This dielectric cap 30 can be acontinuous layer or a discontinuous layer. It can also be a select cap,such as CoWP. The thickness of the dielectric cap 30 may vary dependingon the technique used to form the same as well as the material make-upof the layer. Typically, the dielectric cap 30 has a thickness fromabout 15 to about 55 nm, with a thickness from about 25 to about 45 nmbeing more typical.

The block mask 32 of stack 28 is formed utilizing any conventionaldeposition process including, for example, CVD, PECVD and spin-oncoating. The block mask 32 of stack 28 comprises a standard photoresistmaterial including inorganic, organic and hybrid resists. The block mask32 may further comprise at least one anti-reflective coating layerand/or at least one hardmask layer. The composition of theanti-reflective coating layer and the hardmask layer can be organic,inorganic or organic/inorganic hybrid materials as long as thecombination of their composition and layer thickness satisfies thepatterning and pattern transfer needs of the airgaps 34 and 36 (FIGS. 1Iand 1J).

Next, and as is shown in FIG. 1I, the stack 28 is patterned providing anairgap pattern 34 therein. The patterning step includes opticallithography, immersion lithography, EUV, soft lithography, contactprinting, nano-printing, E-Beam, maskless direct writing, scanning probelithography and self-assemble lithography. Note that the feature size ofthe airgap pattern 34 is less than the metal spacing within the low-kdielectric materials. The patterning step also includes etching such asreactive-ion etching.

The airgap pattern 34 is then transferred into at least the second curedlow-k dielectric material 22′ utilizing a timed etching process such as,for example, reactive ion etching. After transferring the airgap pattern34 into the second cured low-k dielectric material 22′, the remainingblock mask 32 is removed from the structure utilizing a conventionalremoval method of sacrificial materials such as reactive ion etching,stopping atop the remaining dielectric cap 30. This structure isillustrated in FIG. 1J. In FIG. 1J, reference numeral 36 denotes theairgap opening. As is shown, the transferred airgap pattern is adjacentto, but not directly abutting the conductively filled regions formedinto at least the cured second patternable low-k dielectric material.

After transferring the airgap pattern into at least the cured secondlow-k dielectric material 22′, portions of the low-k dielectric materialthat are directly abutting the airgap opening 34 are changed physically,chemically or both so as to have a different removal rate as compared tothe remaining low-k dielectric material. This change in removal rate isachieved in the present application, by a chemical treatment, exposureto a reducing or an oxidizing plasma. One preferred embodiment of thismaterial transformation is by an isotropic reactive ion etching. Theisotropic ion etching gas chemistry is selected from at least one of O₂,CO, CO₂, N₂, H₂, NH₃, He, Ar, hydrocarbon and the like. This changedportion of the low-k dielectric directly abutting the airgap opening isthen removed utilizing an etching process such as, for example, anisotropic etch utilizing a DHF etchant. A supercritical fluid etchingprocess may also be used in some embodiments of the invention. These twosteps, e.g., changing the etch selectivity of portions of the low-kdielectric material and etching, provides an airgap 38 within thestructure. The airgap 38 may include air or a vacuum. A pump may be usedto remove the air from the airgap 38 to form a vacuum. The resultantstructure including the airgap 38 is shown in FIG. 1K.

Next, and as shown in FIG. 1L, an airgap cap 40 is formed atop thedielectric cap 30 sealing the airgap 38 in the structure. The airgap cap40 includes an ARC including a conventional inorganic ARC and theinorganic ARC described above. In a preferred embodiment, the airgap cap40 is the same as the inorganic ARC 16. The composition and method ofits deposition was described above.

In addition to the dual-damascene embodiment mentioned above, thepresent invention also contemplates a single-damascene embodiment.

While the present invention has been particularly shown and describedwith respect to preferred embodiments thereof, it will be understood bythose skilled in the art that the foregoing and other changes in formsand details may be made without departing from the spirit and scope ofthe present invention. It is therefore intended that the presentinvention not be limited to the exact forms and details described andillustrated, but fall within the scope of the appended claims.

What is claimed is:
 1. An interconnect structure comprising: at leastone patterned and cured low-k dielectric material located on an uppersurface of a patterned inorganic antireflective coating that is locatedatop a substrate, wherein said inorganic antireflective coatingcomprises atoms of M, C and H wherein M is at least one of Si, Ge, B,Sn, Fe, Ta, Ti, Ni, Hf and La, said at least one cured and patternedlow-k dielectric material and said patterned inorganic antireflectivecoating having conductively filled regions embedded therein and said atleast one cured and patterned low-k dielectric material having at leastone airgap located adjacent, but separated from the conductively filledregions by a portion of said low-k dielectric material.
 2. Theinterconnect structure of claim 1 wherein said inorganic antireflectivecoating further comprises atoms of O, N, S, F or mixtures thereof. 3.The interconnect structure of claim 1 wherein said at least onepatterned and cured low-k dielectric material comprises a curedfunctionalized polymer having one or more irradiation/acid-sensitiveimageable groups.
 4. The interconnect structure of claim 3 wherein saidfunctionalized polymer comprises a polymer of a hydrocarbon, afluorinated hydrocarbon, a siloxane, a silane, a carbosilane, anoxycarbosilane, an organosilicate or a silsesquioxane.
 5. Theinterconnect structure of claim 3 wherein said functionalized polymerfurther comprises a functionalized sacrificial pore generator.
 6. Theinterconnect structure of claim 1 further comprising a dielectric caplocated on an uppermost surface of said at least one patterned and curedlow-k dielectric material, said dielectric cap having an opening inwhich an upper portion of the at least one airgap extends through. 7.The interconnect structure of claim 6 further comprising an airgap caplocated atop said dielectric cap and atop said opening, wherein aportion of said airgap cap located at said opening is in contact withsaid upper portion of the airgap.
 8. The interconnect structure of claim1 wherein said airgap is filled with air.
 9. The interconnect structureof claim 1 wherein said airgap is a vacuum.
 10. An interconnectstructure comprising: a lower patterned and cured low-k material layerlocated on a surface of a patterned inorganic antireflective coatingthat is located atop a substrate, wherein said inorganic antireflectivecoating comprises atoms of M, C and H wherein M is at least one of Si,Ge, B, Sn, Fe, Ta, Ti, Ni, Hf and La, and an abutting upper patternedand cured low-k material layer located on said lower patterned and curedlow-k material layer, said lower and upper patterned and cured low-kmaterial layers and said patterned inorganic antireflective coatinghaving conductively filled regions and at least said upper patterned andcured low-k film having at least one airgap located adjacent, butseparated from the conductively filled regions by a portion of saidlow-k dielectric material.
 11. The interconnect structure of claim 10wherein said inorganic antireflective coating further comprises atoms ofO, N, S, F or mixtures thereof.
 12. The interconnect structure of claim10 wherein said lower and upper patterned and cured low-k dielectricmaterial layers each comprise a cured functionalized polymer having oneor more irradiation/acid-sensitive imageable groups.
 13. Theinterconnect structure of claim 10 wherein said functionalized polymercomprises a polymer of a hydrocarbon, a fluorinated hydrocarbon, asiloxane, a silane, a carbosilane, an oxycarbosilane, an organosilicateor a silsesquioxane.
 14. The interconnect structure of claim 10 furthercomprising a dielectric cap located on an uppermost surface of saidupper patterned and cured low-k material layer, said dielectric caphaving an opening in which an upper portion of the at least one airgapextends through.
 15. The interconnect structure of claim 10 wherein saidairgap is filled with air.
 16. The interconnect structure of claim 10wherein said airgap is a vacuum.
 17. An interconnect structurecomprising: an inorganic antireflective coating located atop asubstrate, wherein said inorganic antireflective coating comprises atomsof M, C and H wherein M is at least one of Si, Ge, B, Sn, Fe, Ta, Ti,Ni, Hf and La; at least one low-k dielectric material comprising a curedfunctionalized polymer having one or more irradiation/acid-sensitiveimageable groups and located on a surface of said inorganicantireflective coating; at least one conductive structure embedded insaid at least one low-k dielectric material and extending into saidinorganic antireflective coating, wherein an uppermost surface of saidat least one conductive structure is coplanar with an uppermost surfaceof said at least one low-k dielectric material; at least one airgaplocated in said at least one low-k dielectric material, wherein aportion of said at least one low-k dielectric material separates anentire sidewall surface of said at least one airgap from an adjacentsidewall surface of said at least one conductive structure; a dielectriccap located on said uppermost surface of said at least one low-kdielectric material and having an opening in which an upper portion ofsaid at least one airgap extends through, wherein a portion of abottommost surface of said dielectric cap is in direct physical contactwith said uppermost surface of said at least one conductive structure;and an airgap cap located on an uppermost surface of dielectric cap andextending over said opening, wherein a portion of said airgap caplocated at said opening is in contact with said upper portion of said atleast one airgap, and wherein said upper portion of said at least oneairgap does not extend above said uppermost surface of said dielectriccap.
 18. An interconnect structure comprising: an inorganicantireflective coating located atop a substrate, wherein said inorganicantireflective coating comprises atoms of M, C and H wherein M is atleast one of Si, Ge, B, Sn, Fe, Ta, Ti, Ni, Hf and La; a lower low-kdielectric material layer comprising a first cured functionalizedpolymer having one or more irradiation/acid-sensitive imageable groupsand located on a surface of said inorganic antireflective coating; anupper low-k dielectric material layer comprising a second curedfunctionalized polymer having one or more irradiation/acid-sensitiveimageable groups and located directly on a surface of said lower low-kdielectric material layer; at least one conductive structure embedded insaid upper and lower low-k dielectric material layers and extending intosaid inorganic antireflective coating, wherein an uppermost surface ofsaid at least one conductive structure is coplanar with an uppermostsurface of said upper low-k dielectric material layer; at least oneairgap located in said at least said upper low-k dielectric materiallayer, wherein a portion of said upper low-k dielectric material layerseparates an entire sidewall surface of said at least one airgap from anadjacent sidewall surface of said at least one conductive structure; adielectric cap located on said uppermost surface of said upper low-kdielectric material layer and having an opening in which an upperportion of said at least one airgap extends through, wherein a portionof a bottommost surface of said dielectric cap is in direct physicalcontact with said uppermost surface of said at least one conductivestructure; and an airgap cap located on an uppermost surface ofdielectric cap and extending over said opening, wherein a portion ofsaid airgap cap located at said opening is in contact with said upperportion of said at least one airgap, and wherein said upper portion ofsaid at least one airgap does not extend above said uppermost surface ofsaid dielectric cap.